Method and apparatus for roller lubrication

ABSTRACT

The invention relates to a method for lubricating rollers, particularly for lubricating the nip in a roll stand for a rolled strip, wherein water is supplied via at least one first supply line ( 1 ), and oil is supplied via a second supply line ( 2 ) to at least one mixing element ( 3 ). The water and oil are mixed in the mixing element ( 3 ), and the mixture of water and oil is supplied to a spraying element ( 4 ), by means of which the mixture is sprayed onto at least one working roller ( 5, 6 ) or support roller ( 12, 13 ) of a roll stand ( 7 ). In order to ensure a reproducible supply of the rollers with the water/oil mixture in an efficient manner, the invention proposes that a cleaning medium, such as hot water or water vapor be supplied via at least one third supply line ( 8 ) of one of the two other supply lines ( 1, 2 ), and/or of the mixing element ( 3 ) at defined time intervals, or as a function of a process status of the rolling process. The invention further relates to a device for lubricating rollers, particularly for carrying out the method.

The invention relates to a method for roller lubrication, in particularfor lubricating the roller gap in a rolling stand for rolled strips, inwhich water is supplied via at least a first feed line and oil issupplied via at least a second feed line to at least one mixing element,wherein the water and the oil are mixed in the mixing element andwherein the mixture of water and oil is supplied to a spraying elementwith which the mixture is sprayed onto at least one roller of a rollingstand. Furthermore, the invention relates to an apparatus for rollerlubrication, in particular for carrying out the method.

Roller gap lubrication systems are often installed in roiling trains.These are used for the purpose of improving the surface quality of theworking roller and the strip and are included in the normal equipment ofa modern rolling train on which high-quality strips are to befabricated.

The system in which water as the carrier medium and oil are mixed justupstream of the roller and applied to the working roller or supportroller and ultimately take effect in the roller gap is the mostwidespread owing to its simplicity. DE 10 2004 006 130 [CA 2,547,960],EP 1 399 276 [U.S. Pat. No. 7,266,984], EP 1 399 277 [U.S. Pat. No.7,159,433], EP 0 367 967 [U.S. Pat. No. 5,090,225] and WO 2007/025682[CA 2,618,836] disclose solutions of this type.

After a certain operating time, however, the effectiveness of thelubrication is reduced or the results of the roller gap lubricationcannot be reproduced. The lubrication effect is also often uneven overthe width of the strip, which leads to problems in the movement of thestrip. The cause of this is often that the piping between the oil/watermixer and the spray nozzles becomes clogged in layers as a result ofsaponification. Blockages of the small nozzles also occurs whenparticles become detached from the wails and float in front of thenozzle outlet.

A relatively large outlay on maintenance is necessary as a result ofmechanical cleaning of the system or periodical rinsing of the pipingbetween the oil/water mixer and the nozzles and blowing the nozzlesclear.

JP 7016621 discloses periodically stopping the oil supply and carryingout a rinse of the nozzles with the water which is also used for formingthe oil/water mixture.

JP 56139213 provides for a cleaning solution to be able to be introducedinto the fluid lines as required in order to clean them.

In order to reduce the saponification of the roller gap lubricationsystem, particular demands are additionally made of the water quality orwater analysis, which however makes water consumption considerably moreexpensive. In order to adapt the oil to the water quality, additives areadded to the oil. These vary in their composition and effect in thedifferent water qualities worldwide. Determining the oil composition isexpensive, which along with the additives themselves ultimately has adetrimental effect on oil costs. Despite the expense, the oil is notalways adapted optimally to the water used.

The invention is therefore based on the object of creating a method andan associated apparatus with which it is possible to ensure in a simpleand efficient manner continuous roller gap lubrication which has aconstant quality over time. This is to be made possible in a mannerwhich is simple and as environmentally friendly as possible. Inaddition, the process should not be detrimentally effected by it.

The solution of this object by the invention is characterized accordingto the method in that hot water, steam or a chemical detergent, or acombination of two media, is supplied via at least a third feed line tothe first or the second feed line and/or to the mixing element atdefined time intervals or as a function of a status of the rollingprocess.

Hot water or steam or other cleaning media are preferably suppliedduring the change of a roller of the rolling stand or at the end of arolling program before a relatively long, different type of systemstoppage.

Furthermore, the cleaning procedure takes place with for example hotwater following a rolling incident within the rolling train in order toremove any oil residues on the rollers.

The supplied hot water preferably has a temperature of at least 60° C.The hot water or steam is advantageously supplied over a period of 2 to15 minutes.

A detergent, in particular a chemical detergent, can additionally orperiodically be added to the hot water or steam, which detergent iscapable of dissolving stubborn oil residues.

In the event of interrupted supply, hot water or steam is preferablydelivered in the first or in the second feed line.

A warning signal can be output during the delivery of hot water or steamin order to prevent the risk of staff being scalded.

The water can be heated or the steam can be generated by means of anelectric heating element, by means of oil or gas heating or by means ofsolar energy (where applicable only auxiliary). Heating takes placeduring rolling and is available for cleaning on request.

The apparatus according to the invention for roller lubrication ischaracterized in that at least one third feed line is present, which isconnected fluidically at one end to at least one of the first or secondfeed lines and/or to the mixing element and which is connected at itsother end to a feed unit for hot water or steam.

The feed unit for hot water or steam can have at least one electricheating element, oil or gas heating or solar heating. For energy savingreasons, the feed unit (container) is advantageously thermallyinsulated.

The at least third feed line is preferably also at least partiallyprovided with thermal insulation.

Finally, a development provides for the feed unit for hot water or steamto be able to be coupled fluidically to the first feed line for water.

In systems which have a variable flow admittance and have valvesinstalled for this purpose, the valves are cleaned as well. To this end,all valves are opened and the cleaning is carried out over the entiregauge.

With this cleaning technology, the roller gap lubrication system canalso be operated with water and/or oil of relatively low quality, whichis more cost-effective and therefore more economical altogether.Furthermore, the conditions for lubricating the roller gap can always bereproduced.

An exemplary embodiment of the invention is shown in the drawing. Thesingle FIGURE schematically shows an apparatus for roller gaplubrication in a rolling stand for rolled strips, which apparatus isequipped with an integrated cleaning device.

The FIGURE shows an apparatus with which a roller gap is lubricated witha water/oil mixture. A rolling stand 7 is shown schematically, in whichtwo working rollers 5 and 6 interact and form a roller gap, with theworking rollers 5, 6 being supported by support rollers 12 and 13. Astrip 14, which is rolled in the rolling stand 7, is also schematicallyshown.

Two feed lines 1 and 2 are provided in order to feed the rollers and theroller gap with lubricating fluid. The feed line 1 delivers water from asource which is not shown, while oil is supplied via the feed line 2.Both the water and the oil are supplied to mixing elements 3 in whichthe two fluids are mixed. The mixture is then conducted to sprayingelements 4 in the form of spraying bars and sprayed via the latter ontothe rollers 5, 6.

Water shutoff valves 15 are arranged in the first feed lines 1, whichvalves can be actuated by a central controller 16 (indicated by thedashed lines). Similarly, the oil flow in the second feed line 2 canalso be influenced by the controller 16. To this end, oil pumps 17 arearranged in the second feed line 2. These deliver an oil flow to themixing elements 3, wherein they build up their pressure againstnon-return valves 18. Alternatively, switchable open/close valves, whichopen when the oil pumps 17 are actuated, can be arranged instead of thenon-return valves 18.

It is essential that a cleaning medium such as hot water or steam issupplied via at least one third feed line 8 to the first or the secondfeed line 1, 2 and/or to the mixing element 3 at defined time intervalsor as a function of a status of the rolling process.

For this purpose, a feed unit 9 for hot water or steam is provided,which feeds its medium into the third feed line 8. Shutoff valves 19 arealso arranged in the third feed line 8, which valves can be actuated bythe central controller 16. So that the loss of temperature from the feedunit 9 as far as the mixing element 3 is as low as possible, thermalinsulation 11 is provided, which is placed around the line 8.

The hot water or the steam can in principle be generated in the feedunit 9 in any desired manner. In the exemplary embodiment an electricheating element 10 is provided. The water in the feed unit can therebybe heated to temperatures between 60 and 95° C.

In order to prevent the mixing elements 3 and/or the spraying elements 4from becoming clogged, automatic maintenance and cleaning of the rollergap lubrication system is provided. The system is easy to manage andintegrated in the overall automation system of the rolling mill. To thisend, the region between the mixing element (oil/water mixer) 3 and thespraying element (nozzle) 4 is regularly cleaned with hot water or withsuperheated steam, where necessary with addition of chemical detergents,for which a time of approx. 5 minutes is typically to be estimated.

It has been shown that saponification in the lines can be dissolvedagain if hot water with a water temperature of at least 60° C. is used.

The cleaning process is carried out automatically after every use of theroller or a predetermined number of uses of the roller (rollingprograms), or after every use of the roller gap lubrication or apredetermined number of uses, so that a saponification layer whichbecomes thicker and thicker cannot form, but rather the thin layer isremoved again every time after use.

The following procedure is preferably provided:

When the roller gap lubrication is used during the rolling process, thecold water flows constantly through the first feed line 1 and throughthe mixing elements 3 and exits through the spraying elements 4. The oilpumps 17 open the non-return valves 18 by means of the pressure and theoil enters the mixing elements 3, mixes with the water and exits thespraying bar 4 as a dispersion. The dispersion is applied in theexemplary embodiment to the upper and lower working rollers 5, 6 oralternatively to the support rollers (spraying bar not shown), by meansof which the oil reaches the roller gap.

At the end of any rolling program, directly after the last strip exitsthe rolling train, the cleaning procedure of the roller gap lubricationis automatically started. This is possible without disrupting operationwhile a roller is being changed or temporarily changed. The stands to becleaned are selected by means of a process model as a function inparticular of the quantity of oil used, of the activation of the rollergap lubrication and of the duration of cleaning during the laststoppage. The duration of cleaning can be set between 2 and 15 minutes.

The oil pumps 17 are switched off or are already switched off here. Thesupply of cold water via the first feed line 1 is switched off (watershutoff valve 15 closed). The supply of warm water is activated for thepreviously specified time for cleaning. Cleaning is switched off afterthe time has elapsed or can be switched off manually by the user.

The cleaning process for one or a plurality of stands 7 is started bymeans of a process model or automation or else manually by a user. Tothis end, the shutoff valves 19 open and the hot water can flow out ofthe heat-insulated warm water container 9 via the shutoff valves 19through the oil/water mixer 3 and exits likewise at the spraying bar 4.So that the loss of heat from the water is not too great duringtransport from the warm water container 9 to the nozzle bar 4, the feedline 8 from the warm water container 9 to the nozzles 4 is surroundedwith the said heat insulation 11.

During cleaning with the hot water or alternatively with the steam, awarning lamp on the rolling stand 7 is automatically activated, in orderto preclude staff being scalded.

Once the predetermined time has elapsed or the roller change hasfinished, the cleaning of the roller gap lubrication system isdeactivated again and the roller gap lubrication is switched back tooperational.

As mentioned, the heating in the warm water container 9 is electrical.Alternatively, oil or gas heating with or without solar-support is alsopossible. The use of waste heat is likewise possible.

Regular, automatic cleaning of the roller gap lubrication by means of acleaning medium can therefore take place. Cleaning preferably takesplace at the start of any break in rolling or after a defined number ofbreaks in rolling.

The cleaning cycle is preferably controlled and monitored by a processmodel as a function of the oil quantity, of the activation of the rollergap lubrication etc.

The cleaning medium is supplied in the roller gap lubrication systemupstream of the oil/water mixer 3 itself, so that the region between themixer 3 and the exit nozzle 4 can be rinsed.

Any stand can be cleaned individually or together in groups.

Hot water with a temperature of more than 60° C. or steam isadvantageously provided as the cleaning medium, with it being possibleto add a chemical oil-dissolving agent.

The use of normal (filtered) water quality is possible for the rollergap lubrication.

The respective cleaning duration for each stand 7 can be stored orlogged and used for making decisions about the next cleaning procedure.

LIST OF REFERENCE SYMBOLS

-   -   1 first feed line    -   2 second feed line    -   3 mixing element    -   4 spraying element (spraying bar)    -   5 roller    -   6 roller    -   7 rolling stand    -   8 third feed line    -   9 feed unit for hot water or steam    -   10 electrical heating element    -   11 thermal insulation    -   12 support roller    -   13 support roller    -   14 strip    -   15 water shutoff valve    -   16 central controller    -   17 oil pump    -   18 non-return valve    -   19 shutoff valve

1. A method for roller lubrication, in particular for lubricating theroller gap in a rolling stand for rolled strips, in which water issupplied via at least a first feed line and oil is supplied via at leasta second feed line to at least one mixing element, wherein the water andthe oil are mixed in the mixing element and wherein the mixture of waterand oil is supplied to a spraying element with which the mixture issprayed onto at least one working roller or support roller of a rollingstand wherein a cleaning medium such as hot water or steam is suppliedvia at least one third feed line to one of the two other feed linesand/or to the mixing element at defined time intervals or as a functionof a status of the rolling process.
 2. The method according to claim 1wherein hot water or steam is supplied while a roller of the rollingstand is being changed.
 3. The method according to claim 1 wherein thehot water is supplied at a temperature of at least 60° C.
 4. The methodaccording to claim 1 wherein the hot water or the steam is supplied overa period of from 2 to 15 minutes.
 5. The method according to claim 1wherein a detergent is added to the hot water or to the steam.
 6. Themethod according to claim 1 wherein in the event of interrupted supply,hot water or steam is delivered in the first or in the second feed line.7. The method according to claim 1 wherein a warning signal is outputduring the delivery of hot water or of steam.
 8. The method according toclaim 1 wherein the water is heated or the steam is generated by meansof an electric heating element.
 9. The method according to claim 1wherein the water is heated or the steam is generated by means of oil orgas heating.
 10. The method according to claim 1 wherein the water isheated or the steam is generated by means of solar energy.
 11. Themethod according to claim 1 wherein a control unit regularlyautomatically starts the cleaning of the roller lubrication system,determines the rolling stand to be cleaned in a multi-stand rollingtrain and monitors and stores the duration of cleaning.
 12. The methodaccording to claim 1 wherein the cleaning of the roller lubricationsystem is activated at the beginning of every nth roller change, after arolling incident within the rolling train or at the end of a rollingprogram before a system stoppage, or manually by a user.
 13. The methodaccording to claim 1 wherein a single hot water tank, which is providedfor all the rolling stands, feeds the individual rolling stands in turn.14. The method according to claim 1 wherein the cleaning procedureproceeds in the following main method steps: deactivation of the oilpumps; switching off of the cold water supply of the lubrication system;determination of the rolling stand to be cleaned and the cleaning time;activation of the supply of warm water, steam and/or a detergent for theentire spraying width; deactivation of the warm water supply after thecleaning time has elapsed; activation of the cold water supply of thelubrication system; and switching of oil pumps back to operational. 15.An apparatus for roller lubrication, in particular for lubricating theroller gap in a rolling stand for rolled strips, which has at least onefirst feed line for water and at least one second feed line for oil,wherein both feed lines lead to at least one mixing element in whichwater and oil can be mixed, and wherein the mixing element isfluidically connected to a spraying element with which the mixture ofwater and oil can be sprayed onto at least one roller or the supportroller of the rolling stand, in particular for carrying out the methodaccording to claim 1 wherein at least one third feed line is present,which is connected fluidically at one end to at least one of the firstor second feed lines and/or to the mixing element and which is connectedat its other end to a feed unit for hot water or steam.
 16. Theapparatus according to claim 15 wherein the feed unit for hot water orsteam has at least one electric heating element.
 17. The apparatusaccording to claim 15 wherein the feed unit for hot water or steam hasat least one oil or gas heating system.
 18. The apparatus according toclaim 15 wherein the feed unit for hot water or steam has at least onesolar heating system.
 19. The apparatus according to claim 15 whereinthe feed unit and the third feed line are at least partially providedwith thermal insulation.
 20. The apparatus according to claim 15 whereinthe feed unit for hot water or steam can be coupled fluidically to thefirst feed line for water.